This invention relates to an apparatus and method that measures the coordinates of points in three dimensional space. More particularly, the apparatus and method of this invention relates to a kinematically and/or semi-kinematically positioned measuring device that tracks its own location and orientation, allows a user to measure the coordinates of points from any desired location, and acts as a direct link and input device to a computer for processing and viewing data as it is acquired.
Data on the spatial characteristics of both man made and natural objects is valuable and useful for many purposes. Surveyors use data on the physical location of the features of the earth when they create maps and plans. The maps and plans are then used by developers, landowners, government employees, and numerous other persons that require accurate and concise visual descriptions of the spaces and objects. Architects and engineers use models and drawings in the construction and renovation of structures and spaces. Real estate sales persons use drawings of land and buildings as sales and leasing tools. Facility and asset managers use models to track and manage large facilities and their contents.
These and other create a need for accurate and inexpensive input data. In the case of existing buildings, drawings are often used as sources of input data. In the case of spatial scenes such as accident or crime sites or in the case of buildings without existing drawings and similar instances where spatial information is of value, input data must be obtained through physical measurements and then converted to drawings or other means of display. Heretofore, the most accurate way to acquire the desired data has been the use of formal surveying tools and techniques to measure the spatial characteristics of the land or buildings. These techniques, although generally accurate, have proven to be inappropriate in many situations because of the high cost of performing the work involved in taking the measurements and the difficultly in converting the raw data to a useable form.
Currently used surveying techniques have been in use for many, many years and have changed little in concept over time. Surveyors still use transits, theodolites, and other similar devices to record the horizontal and vertical angles from a stationary traverse point to a measured point. The distance from the traverse point to the measured point must also be measured in order to calculate the relative locations of the traverse point and the measured point. Traditionally, distances are measured manually with a tape measure or the like. More recently, electronic distance measuring devices (EDM) have been used to more accurately and easily measure the distances between points.
U.S. Pat. No. 4,295,201 to Wiklund disclosed a device for mapping an area. The device, in its preferred embodiment, was mounted on a tripod and comprised an electronic distance meter, a vertical angle unit, a horizontal angle unit that included a detector that detected the earth's magnetic field, and a calculating unit. The device used the earth's magnetic field to compute the distance from a fixed point to a measuring point on an object and the direction from the fixed point to the measuring point in the horizontal plane relative to a reference direction.
U.S. Pat. No. 4,205,385 to Ericson, et al. disclosed a surveying system comprising a theodolite, a level sensor, and an on board microcomputer that can be used in conjunction with an electronic distance measuring instrument. The device translated raw data, comprising horizontal angle, vertical angle, and slope range, into the more useful components of horizontal distance, latitude, departure, and elevation.
U.S. Pat. No. 5,091,869 to Ingram et al., disclosed a method for creating a two dimensional floor plan of an existing building. The Ingram et al. device used an electronic distance measuring device, a theodolite, and a data collector to measure the angles and distances to prominent points on walls from a traverse point. The data collector stored the data for a subsequent transfer to a separate and remote computer. In a separate operation, the computer used the data to create a two dimensional floor plan.
All of these devices suffered the same shortcomings. The measurements were taken from a stationary traverse location that was fixed relative to the area or object being measured. Although multiple traverse locations could be established and measurements could be taken from those traverse locations, the measuring devices had to be precisely positioned at each traverse point so that points measured from that traverse location could be referenced to a global reference frame. The requirement of a stationary traverse location made the process of measuring the physical location of points tedious, time consuming, and expensive. Additionally, the user could not view his or her work as it progressed for verification and correction since these devices do not operate as real-time input devices for computers and applications software. Further, these devices did not locate the measured points in three dimensions, they only produced angle and distance measurements. Thus, additional external calculations were required to calculate the location of measured points in three dimensions.